Signal processsing apparatus

Claim 1

APPARATUS FOR DETERMINING THE RELATIVE TIME DISPLACEMENT BETWEEN TWO COHERENT ELECTRICAL ALTERNATING CURRENT SIGNALS COMPRISING: CONTROL MEANS FOR PROVIDING A REFERENCE POTENTIAL LEVEL; FIRST MEANS RESPONSIVE TO SAID CONTROL MEANS TO PROVIDE A PULSE-LIKE OUTPUT SIGNAL EACH TIME THE FIRST OF SAID ALTERNATING CURRENT SIGNALS PASSES THROUGH SAID REFERENCE POTENTIAL LEVEL; SECOND MEANS RESPONSIVE TO SAID CONTROL MEANS TO PROVIDE A SECOND PULSE-LIKE OUTPUT SIGNAL EACH TIME THE SECOND OF SAID TWO ALTERNATING CURRENT SIGNALS PASSES THROUGH SAID REFERENCE POTENTIAL LEVEL; AND THIRD MEANS COUPLED TO SAID FIRST AND SECOND MEANS FOR COMBINING SAID OUTPUT SIGNALS FOR PROVIDING A RESULTANT OUTPUT SIGNAL REPRESENTING THE FREQUENCY OF OCCURRENCE OF SAID PULSE-LIKE OUTPUT SIGNALS OF BOTH SAID FIRST AND SECOND MEANS WITHIN A PRESELECTED TIME INTERVAL, SAID FREQUENCY OF OCCURRENCE BEING AN INDICATION OF THE RELATIVE TIME DISPLACEMENT BETWEEN SAID COHERENT TWO ALTERNATING CURRENT SIGNALS.